There are a range of clinical syndromes that require some form of mechanical ventilation therapy with elevated concentrations of inspired oxygen. These syndromes include hypoxemia, various forms of respiratory insufficiency, and congestive heart failure. Ventilators that treat these conditions provide ventilatory support for the lung, and typically deliver elevated concentrations of oxygen to help oxygenate the organs. The oxygen supplies used as inputs to these ventilators are typically compressed oxygen gas in cylinders or a hospital's compressed oxygen supply piped into the treatment room. More recently, attempts have been made to tee oxygen into a ventilator from an oxygen concentrator, which makes 92% oxygen from room air. In general, even the most portable ventilation therapy systems have limited portability due to the size and weight of the ventilator. Additionally, if the patient requires elevated concentrations of oxygen, also because of the size and weight of the oxygen cylinder that is required as input to the ventilator. Because of this, a large number of patients that need ventilatory support choose not to have it because they do not want to be immobilized by being connected to a conventional ventilator. To solve this dire unmet need, recently, a unique new ventilation system has been devised (U.S. Pat. Nos. 7,487,778, 7,533,670 and 7,588,033) that works using non-conventional gas delivery and patient interface principles, which render the ventilation and oxygen supply equipment highly portable, and in fact wearable. Thus, for the first time, patients that require mechanical ventilatory support can have that support while conveniently and easily ambulating.
Separate from mechanical ventilation therapy, there are also clinical syndromes that require oxygen therapy, but not necessarily ventilatory support. These oxygen therapy systems include compressed oxygen gas in cylinders, oxygen concentrators, and liquid oxygen (LOX) systems. These liquid oxygen systems store oxygen in liquid form, and over time the liquid oxygen converts to gaseous oxygen before being delivered to the patient as gaseous oxygen. LOX can be very advantageous in that it has a more efficient gas volume to storage volume ratio. A liter of LOX typically creates about 800 liters of gaseous oxygen at atmospheric pressure, whereas one liter of compressed oxygen gas in a cylinder typically creates about 100 liters of gaseous oxygen at atmospheric pressure.
In the ambulatory mechanical ventilatory support system described in U.S. Publication Nos. 2008/0135044, 2010/0252042, 2010/0252041, 2010/0252040, 2010/0252039, 2010/0252037, use of LOX has been described for (A) an oxygen supply for a mechanical ventilator, and (B) to use the gas pressure created by a LOX system to power a pneumatically powered ventilator. The advantage of using LOX as an input to a mechanical ventilator is that it can help make the ventilation system highly portable, which is very useful in many clinical applications such as chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), some neuromuscular diseases, as well as field and pandemic uses. However, to be technically feasible to use a LOX system for the input into such a ventilator, the LOX system, the ventilator, or both, requires special unique features.
In summary, existing mechanical ventilation therapies have the following disadvantages: they do not offer respiratory support in an ambulatory form factor that can be easily borne or worn by the patient.